A six or seven gear double clutch transmission is known from the printed publication DE 103 05 241 A1. The double clutch transmission comprises two clutches, which are each connected to the driveshaft at the input sides thereof, and to one of the two transmission input shafts at the respective output sides thereof. The two transmission input shafts are arranged coaxially to each other. Further, two countershafts are arranged axially parallel to the two transmission input shafts, the idler gears of which are combing together with the fixed gears of the transmission input shafts. Furthermore, coupling devices are connected in an axially displaceable, rotationally fixed manner on the countershafts in order to be able to shift the respective toothed gearwheels. The respectively selected transmission ratio is transferred to a differential via the output gears. In order to realize the desired transmission ratio steps in the known double clutch transmission a plurality of gear planes such that a significant amount of construction space is required during installation.
Furthermore, a spur gear multi-speed transmission is known from the printed publication DE 38 22 330 A1. The spur gear multi-speed transmission comprises a double clutch that can be switched under load, one part of which is connected to a driveshaft, and another part of which is connected to a hollow driveshaft that is rotationally supported on the driveshaft. For certain transmission ratios the driveshaft may be coupled to the hollow driveshaft via a shift element.
A power-shift transmission having two clutches is known from the printed publication DE 10 2004 001 961 A1, which are each associated with a subtransmission. The transmission input shafts of both subtransmissions are arranged coaxially to each other and engage idler gears of the associated countershafts with fixed gears. The respective idler gears of the countershafts may be connected to the respective countershaft by means of associated shift elements in a rotationally fixed manner. An eight-shift transmission is known from the printed publication, wherein a further shift element is provided for coupling the two transmission input shafts in order to realize a further transmission ratio step. The eight-shift transmission in this embodiment requires at least six gear planes in both subtransmissions in order to realize the transmission ratio steps. This leads to an undesired elongation of the construction length in the axial direction such that the possibility of installation into a vehicle is substantially limited.
A further power-shift transmission is also known from the printed publication DE 10 2005 028 532 A1, which comprises two input shafts and only one countershaft. This nine-shift transmission requires at least seven gear planes in order to realize the transmission ratio steps. This leads to undesired elongation of the construction length in axial direction. Furthermore, an additional shaft having a gear plane is required in order to realize the reverse transmission ratios, which comprises a shift element and two toothed gears. A further disadvantage arises in the known power-shift transmission in that power shifts are possible only between the first and the second gears.